Thank you again.
Take the case of a turntable sitting on a vibration mitigating platform (VMP) and that platform sitting on a rack. I say VMP because that platform seems to do or want do two things: damping and isolation.
1. It wants to isolate the turntable from vibrations coming from the floor or through the rack, by turning them back or prevent them from entering itself.
2. It wants to damp by allowing vibrations coming from the turntable to enter into itself, to burn them up.
You note real life solutions are usually a mix of the two.
I speculate an effective VMP would or could contain different 'systems' for these two jobs and no single system optimally could do both. Or is that incorrect thinking?
Hi Tima,
My pleasure
Re 1. First and foremost It wants to prevent external vibrations from reaching TT. How it does it - isolates, damps, both, in what proportions, by which mechanism it's in a sense secondary.
Re 2. I have no idea where all this obsession with damping internally generated vibrations by external means come from. Internal damping of the device is
the job of the device designer. Sometimes something can be improved here by e.g. tight coupling to a massive, well damped platform. Then if one can divert internally generated vibrations to the platform, it will get burned there (a caveat - whatever marketing magitians say there is no "vibrations diode", vibrations travel both ways by their nature so be careful).
Yes, combining different systems is the way to go. For example in our 2-stage Advanced platform (if I may use it as an example being most familiar with), moving from ground up:
- pneumatic suspension to isolate at LF
- the suspension is additionally pneumatically damped to burn some of the vibrational energy in air pushing and expansion/contraction cycles
- high mass as damping at upper LF (most difficult region) - vibrations burn their energy moving a high mass; the higher the mass, the lesser the movement with the same vibrational energy
- CLD damping from lower MF up - burning vibrational energy in metal/viscoelastic lossy layer/slate composite; slate itself also provides some of CLD damping
- highly sensitive hardened steel bearings to addionaly isolate in the horizontal plane; the lower bearing racings damped at MF by embedding in the slate
- one more layer of CLD damping - the top bearing racings are embeded in a massive 32kg metal/viscolayer/slate plate
Cheers,